creddit: libreddit: Create folders in PREFIX if they don't exist

If we run into the case that the folders /bin, /lib, /include, etc.
don't exist in our PREFIX, then we need to make then using MKDIR.
make install fails without this patch.
creddit: Fix ./common.mk issue, uname was called with wrong parameter

uname was called with the '-r' parameter, which returns the kernel
version. This patch changes it to '-s', which prints the kernel name.
Merge pull request #57 from DSMan195276/macosx-makefile-fix

Macosx Makefile fixes